AC Coupled 101

Like most my grid is up most of the time but I still want a battery based system because when it does go down it's for a week or longer.

Now that XWMPPT80-600 is shipping is AC Coupling as attractive as it used to be?

I don't think I want the hassles of all the work arounds discussed for AC Coupling.

I personally would prefer to have system with components that are designed to work together, UL listed and being used in a manner that is supported by the manufactuter. AC coupling doesn't appear to offer that.

What are some of the other pros and cons of AC Coupled?

Thanks, T

Comments

  • RCinFLARCinFLA Solar Expert Posts: 1,351 ✭✭✭
    Re: AC Coupled 101

    With the XWMPPT80-600 you are going to need the battery capacity to take the ripple current through the batteries. Roughly 100 AH for every kW of PV injected via battery node. The grid push will stress the batteries more then just a normal float charge.

    As to pro and cons, the XW GT AC coupling will inject directly into grid without the double conversion loss (MPPT80 + XW6048 ). It doesn't stress the batteries during normal grid operation power push.

    The way XW6048 deals with PV inverter when grid is down is all or nothing. When battery is full and loads don't consume PV power it moves AC freq off 60 Hz to turn off GT inverter. Second con, again when grid is down, is there is no current regulation on PV power push to battery. What ever the excess PV power, not consumed by AC loads will be pushed to battery, until it reaches full charge. You have to make sure the batteries are large enough AH that the max PV power does not exceed maximum charge rate on batteries (or the power capability of XW inverter).
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: AC Coupled 101
    Altnrgy wrote: »
    Like most my grid is up most of the time but I still want a battery based system because when it does go down it's for a week or longer.

    Now that XWMPPT80-600 is shipping is AC Coupling as attractive as it used to be?

    I don't think I want the hassles of all the work arounds discussed for AC Coupling.

    I personally would prefer to have system with components that are designed to work together, UL listed and being used in a manner that is supported by the manufactuter. AC coupling doesn't appear to offer that.

    What are some of the other pros and cons of AC Coupled?

    Thanks, T
    You might want to look at SMA equipment (Sunny Island and Sunny Boy) for an AC coupled backup system.
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